Compact proton therapy system with energy selection onboard a rotatable gantry

ABSTRACT

Systems and apparatuses for providing particle beams for radiation therapy with a compact design and suitable to a single treatment room. The radiation system comprises a stationary cyclotron coupled to a rotating gantry assembly through a beam line assembly. The system is equipped with a single set of dipole magnets that are installed on the rotating gantry assembly and undertakes the dual functions of beam energy selection and beam deflection. The energy degrader may be exposed to the air pressure. The beam line assembly comprises a rotating segment and a stationary segment that are separated from each other through an intermediate segment that is exposed to an ambient pressure.

CROSS REFERENCE

The present application is a continuation application of U.S. patentapplication Ser. No. 14/033,950, filed on Sep. 23, 2013, entitled“COMPACT PROTON THERAPY SYSTEM WITH ENERGY SELECTION ONBOARD A ROTATABLEGANTRY,” which claims the priority to and benefit of U.S. ProvisionalPatent Application No. 61/798,354 filed on Mar. 15, 2013. The presentapplication claims priority to and benefit of PCT application No.PCT/US14/22092, filed on Mar. 7, 2014, entitled “COMPACT PROTON THERAPYSYSTEM WITH ENERGY SELECTION ONBOARD A ROTATABLE GANTRY,” which claimsthe priority to and benefit of U.S. Provisional Patent Application No.61/798,354 filed on Mar. 15, 2013. The present application is related tothe U.S. patent titled “Irradiation device,” U.S. Pat. No. 8,053,736,filed on Apr. 5, 2007, which claims priority to German patentapplication No. 202006019307.3, file don Dec. 21, 2006. The foregoingpatent applications and patent are hereby incorporated by reference intheir entirety for all purposes.

TECHNICAL FIELD

Embodiments of the present disclosure relate generally to medicaldevices, and more particularly, to radiation therapy devices.

BACKGROUND

In a typical proton therapy system used for tumor radiation treatmentsfor example, a proton beam is produced in a cyclotron or a synchrotronin a specific level of energy that can be adjusted to a prescribedenergy level by virtue of energy selection then provided to a treatmentstation via a beam transportation system. Such a therapy system includesa particle accelerator, such as a cyclotron or a synchrotron, forproviding the particle beam at a specific energy level. The beamtransport system can tune and deliver the particle beam to a radiationstation. At the end of the beam transport system, a rotational gantryassociated with a radiation nozzle delivers the beam onto an irradiationobject, e.g. a tumor of a patient, in a fixed position supported by theirradiation station during operation. Similar systems can be used forother heavy particle radiation treatment, such as neutron, He or C ionbeam.

Typically a beam output from an accelerator has a fixed energy, e.g. 250MeV. Depending on the diagnosis of a patient's condition, for examplethe depth of a tumor to be treated, different patients are prescribedwith different depth doses of radiation. An energy selection system(ESS) is usually used to tune the fixed energy to the prescribed energy,e.g. 170 MeV. Conventionally, an ESS comprises an energy degrader forattenuating the beam energy roughly, followed by a set of energyselection dipole magnets dedicated for fine energy selection byfiltering the undesired traverse emittances, momentum spread and energyspread resulted from the energy degrader. The transport system alsoincludes a plurality of other magnets for beam focusing and steeringpurposes.

Due to the high cost for purchasing and maintaining such a radiationsystem, a medical facility usually uses one accelerator for a pluralityof treatment stations so the high expenditure for the acceleratorfacilities is distributed. FIG. 1 illustrates a configuration of amedical facility that accommodates a proton radiation system 100providing proton beams for multiple treatment stations in accordancewith the prior art. The system 100 comprises a single stationarycyclotron 101 located in a dedicated room 110, a carbon wedge energydegrader 102 disposed in a vacuum component of the beam line, a gantry121 and 122 for each treatment room 131 and 132, and an ESS, severalsets of quadrupole magnets for focusing the beam, e.g. 104, and aplurality sets of bending magnets that directs the proton beams from thecyclotron to respective treatment rooms, e.g. 131 and 132. As shown, theESS of this system is composed of a carbon wedge degrader 102, and twodipole magnets 105 and 106 with an energy slit (not explicitly shown)sitting in between. The dipole magnets 105 and 106 are located proximateto the accelerator 101 and dedicated for selectively passing theparticles with the targeted energy.

In order to supply the particle beams to different rooms located invarious places relative to the accelerator room 110, the system 100 isequipped with long beam lines, e.g. 111 and 112, along different pathsin which dipole magnets are used to change beam directions. For example,dipoles 107 and 108 are used to redirect the particle beam into the room110. The dipole 141 bends the beam by 45° at the entrance of the gantry121. Another dipole 142 bends the beam by 135° and toward the isocenter.Collectively, the two dipoles 141 and 142 in the gantry bends the beamby 90° from the beam line 111.

Although using a multi-station single-cyclotron system is effective todistribute the cost for large medical facilities, the overall cost forsuch a multi-gantry system may be prohibitively high for smallerfacilities that may only need one treatment station. Also, somemulti-station systems do not support simultaneous treatment in multiplestations. This contribute to further disadvantage that a delay at onetreatment station can cause delay at the other station. Among the costlyfactors in the conventional proton radiation system, the dipole magnetsconsume significant expenditure associate with manufacture,installation, control, maintenance, and space that is limited andvaluable in the medical facility.

Moreover, connecting to the stationary cyclotron and the rotatinggantry, the beam line pipe comprises a rotating portion that can rotatealong with the gantry and a stationary or non-rotating portion leadingto the cyclotron, both portions being maintained under continuous lowpressure (vacuum) typically in the 10E-05 mbar range. Conventionally, arotating vacuum seal is used at the beam line connection between thestationary part of the beam line and the rotating part of the beam lineto keep the pipe sealed from outside air during rotation.

SUMMARY OF THE INVENTION

Thus, it would be advantageous to provide a compact proton radiationsystem that has reduced cost and dimension and is feasible for singleroom proton therapy facility. Accordingly, embodiments of the presentdisclosure advantageously provide a radiation system that utilizes a setof dipole magnets on the gantry for the dual purposes of energyselection and redirecting the particle beam. By integrating the energyselection magnets onto the gantry, rather than in a dedicated section ofthe beam line, consumption of cost and space can be advantageouslydecreased, making the system suitable for a compact single-room design.Embodiments of the present disclosure further simplifies a protonradiation system by placing the energy degrader in the atmosphere and byreplacing the vacuum seal with an air gap at the joint between thestationary portion and the rotating of the beam line.

In one embodiment of the present disclosure, a radiation therapy systemfor irradiating an irradiation object with particle beam in apredetermined energy comprises a stationary particle accelerator, a beamline assembly, an energy degrader, and a swiveling gantry assembly. Thebeam line assembly is operable to direct and focalize a particle beamalong a first direction. The energy degrader is operable to attenuatethe energy of the particle beam and may be exposed to an air pressure.The swiveling gantry assembly comprises a set of dipole magnets as wellas additional quadrupole and steerer magnets, all with controllablemagnetic fields, and a collimator disposed in between the dipolemagnets. The set of dipole magnets are operable to select a portion ofthe particle beam with a predetermined energy, and redirect the portionof the beam to a second direction. The set of dipole magnets maycomprise a 45° and a 135° magnet arranged in sequence. The swivelinggantry may be capable of rotating 360° about the first direction and maycomprise a housing that has a first member made of low-Z material and asecond member made of high-Z material. The beam line assembly maycomprise a rotating segment and a stationary segment couple torespective vacuum apparatuses. The rotating segment and the stationarysegment may be separated by an air gap.

The foregoing is a summary and thus contains, by necessity,simplifications, generalizations and omissions of detail; consequently,those skilled in the art will appreciate that the summary isillustrative only and is not intended to be in any way limiting. Otheraspects, inventive features, and advantages of the present invention, asdefined solely by the claims, will become apparent in the non-limitingdetailed description set forth below.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the present invention will be better understood from areading of the following detailed description, taken in conjunction withthe accompanying drawing figures in which like reference charactersdesignate like elements and in which:

FIG. 1 illustrates a configuration of a medical facility thataccommodates a proton radiation system providing proton beams formultiple treatment stations in accordance with the prior art.

FIG. 2 is an exemplary configuration of a medical facility equipped witha single-room proton therapy system in accordance with an embodiment ofthe present disclosure.

FIG. 3 is a side view diagram illustrates the mechanical schematics ofthe compact radiation system equipped with a set of deflection/energyselection magnets and in accordance with an embodiment of presentdisclosure.

FIG. 4 is a 3D view diagram illustrating the exterior mechanicalschematics of the compact radiation system equipped with a set ofdeflection/energy selection magnets and in accordance with an embodimentof present disclosure.

FIG. 5A illustrate a side view of the beam line in that transport theparticle beam from the cyclotron to the gantry in accordance with anembodiment of the present disclosure.

FIG. 5B illustrate a top view of the beam line in that transport theparticle beam from the cyclotron to the gantry in accordance with anembodiment of the present disclosure.

DETAILED DESCRIPTION

Reference will now be made in detail to the preferred embodiments of thepresent invention, examples of which are illustrated in the accompanyingdrawings. While the invention will be described in conjunction with thepreferred embodiments, it will be understood that they are not intendedto limit the invention to these embodiments. On the contrary, theinvention is intended to cover alternatives, modifications andequivalents, which may be included within the spirit and scope of theinvention as defined by the appended claims. Furthermore, in thefollowing detailed description of embodiments of the present invention,numerous specific details are set forth in order to provide a thoroughunderstanding of the present invention. However, it will be recognizedby one of ordinary skill in the art that the present invention may bepracticed without these specific details. In other instances, well-knownmethods, procedures, components, and circuits have not been described indetail so as not to unnecessarily obscure aspects of the embodiments ofthe present invention. Although a method may be depicted as a sequenceof numbered steps for clarity, the numbering does not necessarilydictate the order of the steps. It should be understood that some of thesteps may be skipped, performed in parallel, or performed without therequirement of maintaining a strict order of sequence. The drawingsshowing embodiments of the invention are semi-diagrammatic and not toscale and, particularly, some of the dimensions are for the clarity ofpresentation and are shown exaggerated in the drawing Figures.Similarly, although the views in the drawings for the ease ofdescription generally show similar orientations, this depiction in theFigures is arbitrary for the most part. Generally, the invention can beoperated in any orientation.

Notation and Nomenclature:

It should be borne in mind, however, that all of these and similar termsare to be associated with the appropriate physical quantities and aremerely convenient labels applied to these quantities. Unlessspecifically stated otherwise as apparent from the followingdiscussions, it is appreciated that throughout the present invention,discussions utilizing terms such as “processing” or “accessing” or“executing” or “storing” or “rendering” or the like, refer to the actionand processes of a computer system, or similar electronic computingdevice, that manipulates and transforms data represented as physical(electronic) quantities within the computer system's registers andmemories and other computer readable media into other data similarlyrepresented as physical quantities within the computer system memoriesor registers or other such information storage, transmission or displaydevices. When a component appears in several embodiments, the use of thesame reference numeral signifies that the component is the samecomponent as illustrated in the original embodiment.

DESCRIPTION OF THE INVENTION

FIG. 2 is an exemplary configuration of a medical facility equipped witha single-room proton therapy system 200 in accordance with an embodimentof the present disclosure. The compact radiation system 200 is designedto deliver a proton beam from the stationary cyclotron 201 to anadjacent single treatment room 203. The proton radiation system 200includes an accelerator 201, e.g. a cyclotron as shown, a short beamline 202 transporting the particle beam from the cyclotron 201 to thesingle treatment room 203 along a linear axis, an energy degrader 204disposed in the beam line 202, a single set of dipole magnets 206 and207, and a swiveling gantry 205 operable to deliver a proton beam to thetreatment station through a nozzle in different angles. In thesingle-room configuration 200, the cyclotron can be placed near thetreat room as close as practically possible, and thus the beam line 204can be short and linear, reducing the need for dipole magnets used forreorienting a particle beam. The system may further comprise a pluralityof sets of focusing magnets mounted in the beam path to focus theparticle team.

In contrast to the multi-station system in FIG. 1, the single-roomsystem 200 has a simplified arrangement of dipole magnets as well as theentire transporting system. Particularly, the dipole magnets 206 and 207installed on the gantry 205 undertake the dual functions of energyselection as well as deflecting the particle beam from the beam lineaxis to the isocenter of the treatment station. In the illustratedembodiment, the 45° dipole magnet 206 located at the entry point of thegantry and the 135° dipole magnet 207 downstream can collectively bendthe particle beam by 90° from the beam line 202 axis. At the same time,when the current in the coils of the magnets 206 and 207 is controlledto a precise current according to a target energy level, the magnets 206and 207 in combination with a beam collimator are operable to performthe energy selection function.

By integrating the ESS magnets in the gantry assembly, rather than in adedicated section of the beam line as in the prior art, systemconsumption of cost and space can be advantageously and remarkablyreduced, making the system suitable for a single-room design and moreaccessible to relatively small clinics. A beam optics simulation on thebeam profile along the beam path proves that the simplified magnetsystem as illustrated in FIG. 2 is feasible to provide substantiallyidentical clinical specification, such as beam size and shape forexample, as resulted from a corresponding conventional multi-roomradiation system that has separate dedicated ESS magnets and thedeflection magnets.

The disclosure is not limited by the angles, configurations or locationsof the dual-function magnets. For instance, the magnets may comprisethree 90° magnets that can collectively bend the beam by 90°. However,using the minimum number (two) of dipole magnets to reorient the magnetsfurthers the purposes of cost-efficiency and compact design. A set ofscanning magnets can be used to control the raster scan of the particlebeam. In some embodiment, the scanning magnets 211 can be placed inbetween the set of dual-function magnets 206 and 207. In the illustratedembodiment, the scanning magnets can be placed downstream after themagnet 207 and near the nozzle, which contributes to yet another designfor a smaller gantry.

The magnetic fields generated by the deflection/energy selection magnets206 and 207 can be controlled by software programs to guide the beam aswell as select the beam of desire energy. The software program can beimplemented by any known computer implemented methods. In some otherembodiment, the deflection magnets may comprise two 45° dipole magnetsand collectively bend the beam by 90°. In some other embodiments, thedeflection magnets may collectively bend the beam by 135° or any otherangle. Any other suitable configuration of the deflection magnets can beused to practice the present disclosure. The deflection/energy selectionmagnets can be controlled by software programs to achieve a specificparticle energy dictated by each specific treatment plan.

The present disclosure can be implemented with any type of collimatorsuitable for particle beam energy selection that is disposed downstreamafter an energy selection magnet. The collimator 212 may comprise energyslits, apertures, and/or orifices disposed in between the two magnets206 and 207. In some embodiments, the positions and openings of thecollimators may be controllable. In some embodiments, the collimatorfeatures a compact design, such as an energy selection slit in a slimform, which can advantageously contribute to further reduction in systemconsumption of cost and space.

Still in some other embodiments, the energy selection function can besolely assumed by a combination of suitable magnetic components and oneor more energy degraders, which may advantageously eliminate the needfor a collimator in an energy selection system. For example, a set ofadditional magnets may be used to narrow the spatial cross sectionand/or energy spectrum of the beam that exits from an energy degrader.

In the illustrated embodiment, the energy degrader 204 comprises acarbon wedge disposed under a vacuum chamber situated in the beam line202 and proximate to the accelerator 201. Any other suitable energydegrader can be used to implement the present disclosure. In some otherembodiments, the energy degrader material can be integrated in thegantry as well, and disposed proximate to the deflection/energyselection magnets. In still some other embodiments, the degrader may beexposed to ambient pressure, which can advantageously save cost relatedto material, manufacturing and installation etc. Still in some otherembodiments, the degrader, in conjunction with other magnet fields onthe system, may be configured such that the beam at its exit point has anarrow spatial cross section and energy spectrum, eliminating the needfor a collimator.

The gantry assembly 205 may be rotatable while the accelerator remainsstationary. The system may be equipped with a swiveling device thatrenders the rotations of the gantry such that the particle beam canimpinges on the isocentrically arranged irradiation station in variousdirections. In some embodiments, the gantry can swivel 360° about anaxis that is substantially parallel to the beam line axis such that theparticle beam can impinge on an isocenter in a full circle.

The gantry is coupled to a nozzle operable to emit the particle beamonto the radiation object. The nozzle may be coupled to a set ofdeflection magnets 211 that deflect the beam in mutually orthogonaldirections for purposes of traverse scan, e.g. X-Y scan. The nozzle maybe coupled to means for monitoring beam position and means formonitoring the radiation dose. The nozzle and the focusing magnets mayalso be integrated in the gantry. In some embodiments, the nozzle isrotatable and capable of raster scan in two or three dimensions.

In some embodiments, the nozzle is capable of pencil-beam scan where theparticle beam can be focused on a beam cross-section which liesdistinctly below the size of typical irradiation volumes. The peakdeposition of the radiation dose along the radiation path corresponds tothe Bragg peak location determined by the particle energy. By using asuitable focused pencil beam, many small volumes, so-called voxels, thuscan be irradiated, so that the irradiation volumes of any shape,conformal to the specific shape of a tumor, can be raster-scanned. Thedepth scan can be achieved by varying the particle energy, for examplethrough the ESS.

The gantry may comprise a shielding plug 210 which reduces neutron doserisk near the patient. There may be additional shielding around the beamline. The shielding plug may be a cylindrical sphere or any othersuitable configurations. The gantry may comprise hybrid materials tobalance the cost reduction and protection against undesirable neutrondose risk. In some embodiments, high-Z material shields, such as lead(Pb), are used at places along gantry that would be prevalent toradiation/neutron emission. Cheaper/lighter materials, such as C, can beused in any other places, for example, the part of the gantry that doesnot face the patient.

The present disclosure is not limited to any particular type ofaccelerator or the associated particle source. In some embodiments, theaccelerator may be a cyclotron, for example a superconductingsynchrocyclotron in a compact design. In some embodiments, theaccelerator may be able to provide protons, neutron, electrons, or heavyion, such as He2+ or C6+ particles.

FIG. 3 is a side view diagram illustrates the mechanical schematics ofthe compact radiation system equipped with a set of deflection/energyselection magnets 301 and 302 in accordance with an embodiment ofpresent disclosure.

In some embodiments of a single-room radiation system in accordance withthe present disclosure, the entire beam line, including the rotatingportion leading to the gantry and the non-rotating portion leading tothe accelerator, is under vacuum. The rotating portion and thenon-rotating portion are connected through a vacuum seal. In theillustrated embodiment, the beam is transferred from stationary torotating parts via a small air gap 303 and two thin kapton (polymidefilm) windows for example. Thus, each portion has its own vacuum devicesand independent of the other portion. This advantageously furthersimplifies the system, by eliminating the need for a rotating,mechanical vacuum joint, and reduces material cost, simplifiesmaintenance and less vacuum leaks on the beam pipe.

Besides the components described with reference to FIG. 2, FIG. 3 alsoillustrates the other pertaining components, including storage activatedparts and a PV control alcove, and can be appreciated by those withordinary skills in the art.

FIG. 4 is a 3D view diagram illustrating the exterior mechanicalschematics of the compact radiation system equipped with a set ofdeflection/energy selection magnets 401 and 402 in accordance with anembodiment of present disclosure.

FIG. 5A and FIG. 5B illustrate a side view and a top view of the beamline in that transport the particle beam from the cyclotron to thegantry in accordance with an embodiment of the present disclosure.

Although certain preferred embodiments and methods have been disclosedherein, it will be apparent from the foregoing disclosure to thoseskilled in the art that variations and modifications of such embodimentsand methods may be made without departing from the spirit and scope ofthe invention. It is intended that the invention shall be limited onlyto the extent required by the appended claims and the rules andprinciples of applicable law.

What is claimed is:
 1. A radiation therapy system for irradiating anirradiation object with particle beams of a predetermined energy, saidradiation therapy system comprising: a particle accelerator configuredto provide a particle beam for a single treatment station; a beam lineassembly coupled to said particle accelerator and operable to directsaid particle beam along a first direction; an energy degrader operableto attenuate an energy of said particle beam; and a gantry assemblycoupled to said beam line assembly and comprising dipole magnetsconfigured to generate variable magnetic fields, wherein said variablemagnetic fields are operable to select a portion of said particle beamwith said predetermined energy for irradiating said irradiation objectand redirect said portion of said particle beam to a predetermineddirection.
 2. The radiation therapy system of claim 1, wherein saidvariable magnetic fields are externally controlled by electrical currentin coils surrounding said dipole magnets.
 3. The radiation therapysystem of claim 1, wherein said variable magnetic fields are controlledby a software program based on a prescribed treatment plan.
 4. Theradiation therapy system of claim 1, wherein said energy degrader isdisposed in said gantry assembly, and wherein said gantry assemblycomprises a swiveling gantry configured to rotate up to an angel that isgreater than 180° and less than 270° .
 5. The radiation therapy systemof claim 4, wherein said energy degrader comprises an exit openingconfigured to narrow a spatial crosssection of said particle beamexiting said exit opening.
 6. The radiation therapy system of claim 4,wherein said energy degrader comprises an exit opening configured tonarrow an energy spectrum of said particle beam exiting said exitopening.
 7. The radiation therapy system of claim 4, wherein said gantryassembly comprises no collimator.
 8. The radiation therapy system ofclaim 1, wherein said predetermined direction deviates from said firstdirection by 135°.
 9. The radiation therapy system of claim 1, whereinsaid particle accelerator comprises a superconducting synchrocyclotron.10. The radiation therapy system of claim 1, wherein said particle beamcomprises particles selected from a group consisting of protons,neutrons, He ions and C ions.
 11. The radiation therapy system of claim1, wherein said predetermined direction directs to an isocenter.
 12. Aproton radiation therapy system configured to provide proton beamradiation to a single treatment station, said proton radiation therapysystem comprises: a cyclotron coupled to a proton source; a beam lineassembly coupled to said cyclotron and operable to direct a proton beamto a gantry assembly; an energy degrader operable to attenuate an energyof said proton beam; said gantry assembly coupled to said beam lineassembly and comprising: a plurality of dipole magnet configured togenerate variable magnetic fields, wherein said variable magnetic fieldsare operable to select a portion of said proton beam with apredetermined energy for irradiating said irradiation object and toredirect said portion of said proton beam to a predetermined direction.13. The proton radiation therapy system of claim 12, wherein saidvariable magnetic fields are externally controlled by electrical currentin coils surrounding said plurality of dipole magnets, and wherein saidelectrical current is controlled by a software program based on aprescribed treatment plan.
 14. The proton radiation therapy system ofclaim 12, wherein said energy degrader is disposed in said gantryassembly, and wherein said gantry assembly comprises a swiveling gantryconfigured to rotate in a range of 0˜270°.
 15. The proton radiationtherapy system of claim 12, wherein said energy degrader comprises anexit opening configured to narrow a spatial crosssection of said protonbeam exiting said exit opening.
 16. The proton radiation therapy systemof claim 12, wherein said energy degrader comprises an exit openingconfigured to narrow an energy spectrum of said proton beam exiting saidexit opening.
 17. The proton radiation therapy system of claim 12,wherein said gantry assembly comprises no collimator, and wherein saidcyclotron is a super conducting cyclotron.
 18. The proton radiationtherapy system of claim 12, wherein variable magnetic fields areconfigured to bend said proton beam by 90°.
 19. The proton radiationtherapy system of claim 12, wherein said energy degrader is exposed toatmosphere.
 20. The proton radiation therapy system of claim 12, whereinsaid predetermined direction directs to an isocenter.